It is known that a storage apparatus including a plurality of storage devices includes a control apparatus that performs access control between a host apparatus and the storage devices (for example, refer to Patent Documents 1 and 2).
A storage apparatus sometimes includes a plurality of apparatus, cables or the like of the same type, and makes control devices, paths between the control devices and storage devices and so forth redundant to achieve improvement in availability or performance of the system.
Where a plurality of control apparatus, for example, a plurality of controller modules (CMs), are provided, also it is known that a storage apparatus includes a switch unit for allowing communication between the CMs (for example, refer to Patent Documents 3 and 4). Also with regard to the switch unit, a plurality of switch units may be provided in a storage device so as to be redundant in order to improve the availability and the performance of the system.
It is to be noted that also it is known that, in the storage apparatus described above, the plurality of switch units are coupled to a back panel provided in the storage apparatus (for example, refer to Patent Document 4).
[Patent Document 1] Japanese Laid-Open Patent Application No. 2005-122763
[Patent Document 2] Japanese Laid-Open Patent Application No. 2007-087266
[Patent Document 3] Japanese Laid-Open Patent Application No. 2006-155392
[Patent Document 4] Japanese Laid-Open Patent Application No. 2006-209549
In the storage apparatus described above, since the back panel is not made redundant, if the back panel fails, then operation of the storage apparatus is stopped. For example, after the power supply to the entire storage apparatus is turned off, exchange of the back panel is performed.
In this manner, a storage apparatus that includes a plurality of control devices is sometimes degraded in availability.